when i turn hot tap on boiler will not fire up. if turn ch on dhw works ok. help!

tony, August 2008

hi ive just had the same problem , after changing the diaghphrams in the diverta valve i still had the same problem , the route cause for me was a blocked heat exchanger , i cured this with a cheap morrisons descaler , just removed the heat exchanger flushed as much crap out as possible then soaked in boiling water with the descaler and it came out brand new , flushed it again then refitted , and hay presto the boiler hasnt faulted out as yet , give it a go for a quid spent at morrisons it could be a cheap fix

LIVERPOOL FAN, January 2010

hi guys i have refurbed the diverter valve with the halstead kit , i have also changed the thermister , still now joy , every time i call for hot water it runs hot then the burner cuts out then after a min it fires back up again , has anybody any more ideas what next to try , someone suggested the fan venturi but ive looked at the fan and i dont know what it looks like to clean out , i must stress that there is no issue with the central heating that is absolutly fine
please help

barry, November 2009

hi just changed the diaphram and no joy the hot water comes on for a min or two but then goes off , i have notced that both micro switches are being called at the same time can anybody advise me
thanks barry

barry, October 2009

hi i have taken your advice and ordered a new diaphram for the flow switch , i have also noticed that whan i call for DHW both flow switches turn on for DHW and heating , so i will give it a shot with the new diaphram when it comes tomorrow , i guess its going to be cold showers for a day or so urghhhhhhhhhhhhh if you have any more advice or checks i can do please let me know


thanks barry

barry, October 2009

Just had same problem with DHW and it's a perished diaphragm in the diverter valve....can be replaced without having to buy a new diverter valve unit

Dominic, April 2009

got the same problem phoned halstead and was told needed part no 840505 but no stock !!!!!!

Nigel, December 2008

Most likely to be the diaphragm (located in the brass pancake type casing on RH side of diverter valve,referred to as the flowswitch by Halstead), a service kit is available but very expensive £17 to £31 depending on where you buy. The dhw microswitch is on the LH end of diverter valve, there could possibly be a problem with this, you can actually check visually for operation of microswitch if the valve pin moves fully onto the switch when a hot tap is open the problem will be in the swtch,this can be further verified by disconnecting switch leads and testing switch with a multimeter.

Marvo The Magician, September 2008

flow switch/diaphragm not sure whats on this particular boiler but thats the problem. flow of water not being recognised by boiler so boiler does not fire.

iain, August 2008